Showing papers on "High-bit-rate digital subscriber line published in 2012"

System design of reverse-powered G.fast

Abstract: The continued growth of multimedia traffic pushes access network operators to further boost performance over their copper infrastructure network. As a result, digital subscriber line technology has evolved substantially. Field and lab trials have proven that recent innovations, such as crosstalk cancellation and phantom mode transmission, can push data rates of VDSL2 higher than 100 Mb/s on a single twisted pair and 300 Mb/s on two pairs. In ITU-T Q4, a new access technology to provide aggregate data rates in the range of 500 Mb/s to 1 Gb/s per copper loop of up to a few hundred meters is being defined under the G.fast project. G.fast enables the continued cost-effective deployment of fiber in the access network. In this paper, we give an overview of some key challenges this new access technology needs to overcome. By taking into account the expected access network topology, we give guidelines for the node architecture and deployment of G.fast.

Design of reliable fiber‐based distribution networks modeled by multi‐objective combinatorial optimization

Abstract: SUMMARY In this work, we investigate the planning of hybrid fiber/very high bit rate digital subscriber line (HFV) access networks. This HFV variant is considered as an alternative to passive optical access network. It consists of implementing optical fibers in the access network part from the central office to the street cabinets, whereas the very high bit rate digital subscriber line technology is used in the last meter part, from street cabinets to subscribers. Firstly, we discuss the different tasks of this planning problem. We model this planning problem as a multi-objective optimization problem, where different conflicting objectives have to be optimized at the same time. We consider network costs and network reliability. This problem is solved by two different approaches: the classical single-objective optimization (SOO) and the multi-objective optimization (MOO), which is a recent optimization approach that is gaining an increasing interest in practical optimization problems. MOO solves the problem by searching for different optimal trade-offs between the optimization objectives. The performances of SOO and MOO are analyzed and compared with each other using three network instances. Copyright © 2012 John Wiley & Sons, Ltd.

Digital subscriber line signal processing method, device and digital subscriber line system

Abstract: Disclosed in the embodiments of the present invention are a digital subscriber line signal processing method, a device and a digital subscriber system. The signal processing method comprising: use symbols of frames to be transmitted to carry data to be transmitted; obtain the number of remaining symbols, said remaining symbols not carrying any data to be transmitted and being located within the frame to be transmitted carrying data to be transmitted; within the frame to be transmitted carrying data to be transmitted, add quantitative information of the remaining symbols and send frames carrying data to be transmitted and having quantitative information of remaining symbols. The embodiments of the present invention, by means of adding quantitative information of remaining symbols not carrying data to be transmitted, informs the receiver of the existence of remaining symbols not carrying data to be transmitted. Thus, processing is not executed on remaining symbols, thereby saving processing power for the TDD DSL system, reducing consumption, and causing the TDD DSL system to be energy efficient.

Expert system based on wavelets and DELT measurements for VDSL systems

Abstract: Dual-ended line testing (DELT) is a common capability in most current modems and can be used for digital subscriber line (DSL) qualification and monitoring purposes. In spite of that, this feature remains largely unexplored in the literature. This paper proposes a new method based on wavelets and DELT measurements for estimating the total length of the line under test and identification of bridged-taps, two important line parameters that affect the maximum bit rate reached by a DSL line. The proposed method was tested with measurements employing real twisted-pair cables and obtained reasonably accurate results for the analyzed cases.

Embedded Tutorial ET2: Digital Subscriber Line

Abstract: Digital Subscriber Line (DSL) is a family of standards that allow existing twisted pair copper lines to carry modulated digital signals which uses telephone network and unused frequency Spectrum. In this tutorial we describe DSL (Digital Subscriber Line), comparing with POTS and ISDN. We explain the different DSL flavors available with the modulation techniques used and also discuss challenges in getting high performance and throughput, achieving xDSL rate and meeting the DSL standard. We begin by introducing DSL having a pair of modems CO (Central office) and CPE (Customer Premises Equipment) and talk about frequency spectrums. We explain the limitations of POTS (Plain Old Telephone System) with Dial-up Connection and ISDN (Integrated Services Digital Network), and advantages of DSL over POTS. Next we describe various flavors of DSL with their frequency spectrums, power enhancements, standardization, profiles, and band plans. We discuss different modulation techniques with their advantages and disadvantages, including Single carrier Modulation like CAP and QAM and Multi Carrier Modulation like DMT. We explain the interferers/noise: Line Attenuation, The channel attenuation, Bridged taps, Impulse noise, White noise, NEXT, FEXT, RE Interference. We conclude the tutorial with a description of full activation and initialization phases. The targeted audience for the tutorial is designers, developers, testers, people working in the area of VDSL, ADSL technology and People working on different platforms like DSLAM's, Central office, Customer premises equipment, Gateway products as well as products related to access network who are familiar with copper line and modems.

EVM Based SNR Estimation Performance in Cross QAM Using Selected Constellation Points

Abstract: In this paper, we investigate the signal to noise ratio (SNR) estimation performance of Cross quadrature amplitude modulation (QAM), which is being used for asymmetric digital subscriber line (ADSL), very high bit rate digital subscriber line (VDSL), and digital video broadcasting - cable (DVB-C), and has been found to be useful in adaptive modulation and blind equalization. At first, the symbol error rate (SER) performance of Cross QAM is analyzed in Rayleigh fading channel. Then we suggest error vector magnitude (EVM) based SNR estimation utilizing the selected constellation points having different types of decision region from one another, and verify that SNR estimation performance of each points have different performance pattern through simulation. From the simulation results, it has been found that when suggested selected constellation points are used for SNR estimation in Cross QAM, estimation performance is enhanced in additive white Gaussian noise (AWGN) channel or Ricean fading channel.

Quality-of-service-based interference cancellation in upstream very-high-bit-rate digital subscriber line systems

Abstract: Crosstalk (XT) is the main performance limiter in digital subscriber line (DSL) systems such as very-high-bit-rate digital subscriber line (VDSL) systems. In order to overcome these limitations various XT cancellation techniques have been proposed to mitigate this effect. While leading to very high performance gains, the computational complexity grows quadratically with the number of lines in a binder. This motivates partial cancellation schemes, maximising the capacity based on a given computational complexity. However, the data rate increase could still be very high above the quality of service (QoS) requirements that must be enforced for each user, leading to a `waste` of computational resources. Therefore a QoS-based partial cancellation algorithm is presented in this study which selects the lines to be cancelled based on the desired data rates of the users. It relies on partial zero-forcing XT cancellation but the used selection algorithm [QoS-based joint tone-line selection (QoS-JTLS)] aims at QoS fulfilment instead of data rate maximisation. Simulation results show that compared with other QoS-based algorithms and conventional selection algorithms, QoS-JTLS leads to better fulfilment of QoS demands for the same given computational complexity. In other words, the computational complexity needed to achieve the target data rates of the users is reduced when applying QoS-JTLS.